My boyfriend was a Pro Skater and Pro Snowboarder, (He is from Los angeles, CA but his family is czech) so I just asked him and he recommends traveling to The Alps.
In the Alps four countries converge. Switzerland, France, Italy, and Austria. Each country is unique and there are a lot of factors that can influence the difference of quality out of these countries.
To answer this question further he would focus on your personality type, interests, what time of year you planned to go to Europe to snowboard, your level of experience as well as age. Spain can be great as well.
Don't overlook your own Country, The U.S.A. Has many worthy mountains with snow as well. Here's one great example - Sun Valley in Idaho:
